It is proposed to study mechanisms regulating hypothalamo-pituitary-thyroidal and gonadal function in a variety of physiological conditions with a special emphasis on the late consequences of pathogenic neonatal events. It is planned to test a general theory that the neonatal neuroendocrine control system remains plastic for a brief critical period during which it is subject to organizational influences by normal hormones, foreign substances, and environmental stresses which permanently set its adult regulatory function or "set-point." (1) Pituitary hormones (TSH, GH, LH, FSH, PRL), will be measured in serum and pituitary tissue. TRH and LH-RH testing will be performed. Neonatal treatments will include alcohol, morphine, phisohex, hyper- and hypothyroidism. Special emphasis will be placed on studies of the untreated offspring of both treated females and of treated males mated to normal controls. BIBLIOGRAPHIC REFERENCES: Bakke, J.L., Lawrence, N.L., Robinson, S. and Bennett, J.: Observations on the untreated progeny of hypothyroid male rats, Metabolism, 25: 437, 1976. Bakke, J.L., Lawrence, N.L., Robinson, S. and Bennett, J.: Endocrine studies in the untreated F1 and F2 progeny of rats treated neonatally with thyroxine, Biol. Neonate, 1977, in press.